> For example, currently on x86-64, only the lower 48 bits of a pointer are actu... | Hacker News

Hacker Timesnew | past | comments | ask | show | jobs | submit

		floatboth on July 1, 2019 \| parent \| context \| favorite \| on: Go Slices Are Fat Pointers > For example, currently on x86-64, only the lower 48 bits of a pointer are actually used. The other 16 bits could carefully be used for other information Well, you can't dereference these fat pointers directly on amd64, you have to remove the tag. aarch64 actually has a Top Byte Ignore flag though :)

rocqua on July 1, 2019 [–]

I'd also expect that bit-fiddling on pointers, and then de referencing them, is undefined behavior.

kragen on July 1, 2019 | [–]

In C, yes, but not in amd64 or i386 (or most instruction sets.)

Consider applying for YC's Summer 2026 batch! Applications are open till May 4
Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact